This invention relates to multi-user communication of voice and data.
In wireless cellular communications, a large geographic area is divided into cells, each served by a single base station communicating with multiple users in its cell.
3GPP2, a standards organization developing 3rd-generation wireless communication standards, is developing a new wireless air interface standard called 1xEV-DO, described in Baseline Text for the 1xEV-DO Physical Layer: -2000821-021-1xEV_Phy_Layer_Spec_v21, and Baseline Text for the 1xEV-DO Upper Layers (excluding Physical Layer): C30-20000821-021-114b Editor, 1xEV-DO-Sig.baseline_v55_clean, both available from 3GPP2
This standard supports high-speed data communications between MS""s and their BS (acronyms used in this discussion are defined below) at bit rates of up to 2.457 Mbit/s in the forward link (from BS to MS""s) using only 1.25 MHz of spectrum. However, 1xEV-DO cannot efficiently support delay-sensitive, low-rate traffic, such as voice. One can carry voice packets in a 1xEV-DO system using VoIP, however, such an approach wastes significant amounts of bandwidth since the physical layer packet size of 1xEV-DO is much bigger than the size of VoIP packets.
For convenience, the following acronyms used here have the indicated meanings.
In general, in one aspect, the invention features a method that includes sending data in some time slots of a forward link from a base station to at least one remote station in a wireless communication system, and sending voice information from the base station to the at least one remote station in some other time slots of the forward link, the data being sent in a time division multiple access (TDMA) mode, the voice information being sent in a code division multiple access (CDMA) mode.
Implementations of the invention may include one or more of the following features. The data and voice information may be sent in a manner that is compatible with a remote station that is receiving data from the base station according to the 1xEV-DO standard. The CDMA mode may include assigning more than one Walsh code to a single voice call. The time slots in which voice information is sent may be chosen so that at least every fourth slot is not used for voice information and is available for sending the data. The voice information may be sent to different remote stations. The time slots may be used only as needed for sending voice information. The codes assigned to different remote stations may be allocated different power levels for the voice information. Each code used in a voice time slot may be allocated only enough power to achieve a predetermined voice quality.
Other advantages and features will become apparent from the following description and from the claims.